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The Soundwerx Designs DoodleBug

DoodleBug Construction - Build by Photo 1

The first chip that needs to be installed is IC1, the ADuM 3160. Why this chip first? Because its pins are smallest and it's in the center of the board.. You need clear access to both sides of the chip to solder it properly. Once you add the other parts to the PCB, this will become harder.

Above we see the DoodleBug PCB. It's held in the helping hands with alligator clips and electrical tape on all four corners for protection. Note the "E1" stamp. The DoodleBug PCB's have been electrically tested at the manufacturer (Imagineering). No shorted trace defects to confound your build's trouble-shooting. 

The first thing we need to do is prepare an anchor point for U1: 

Note the arrow. It's pointing to my anchor pad that's been tinned. Make certain the center notch on the ADuM chip is at the top! That orients the chip so that pin #1 is at the top left, as indicated by the silkscreen on the PCB. I've applied a bit of solder to the top right pad. I'm right-handed, so what I'll do is hold the soldering iron to this pad with my right hand, while my left hand is holding the ADuM chip with tweezers. While the solder on the pad is melted, I'll move the ADuM chip into place so that the top right pin is positioned into the melted solder. While still holding the iron and the chip, I'll make certain that the pins line up with both rows of pads on the PCB. I'll also make sure that the extended pads leave a bit of room on the outside of all of the pins (the ADuM chip will be centered).

If you get tired doing this, that's OK. Remove the tweezers and the soldering iron. Take a deep breath and relax. Try again by getting a grip on the chip with the tweezers and then applying the soldering iron to melt the pad again. Try to position the chip as good as you can - it will make the soldering much easier later on. Plus, you only have one bit of solder and pad to worry about in this step, so you can keep re-trying as much as you want. Even then, if the chip is a little rotated, you can actually twist it slightly on the PCB when the solder is cooled. Just work with it as long as you need to get it in the right position.

Here we see IC1 in place. The arrow is pointing to the soldered "anchor" pad (the only one right now). The notch is hard to see in this photo, but is at the top center of the chip, making the top left pin, pin #1 (as on the silkscreen).

If you're happy with the positioning of IC1, then what we need to do next is to solder an opposite pad, locking IC1 into place. Once that's done, simply continue on with soldering each pin until complete.

This chip is not nearly as difficult to solder as many DAC chips. For those of you with SMD-soldering experience, the ADuM chip is just like soldering an SOIC-8 opamp. The basic difference is that the ADuM chip is much larger with more pins, but the pin spacing - and therefore, soldering - is much more forgiving than DAC chips. You shouldn't need any special method of soldering. Simply solder each pin to pad separately until you get them all done:

Now that IC1 is soldered, we'll proceed with soldering the small 1206-series SMD capacitors, resistors, and ferrites. The first step in doing this is to "tin" all the pads on one side as shown in this pic (forgot to do C4 anc C7 in this photo):

Here I've soldered C2, C3, and C8 in place. (Again, I forgot to do C4 and C7, but will end up catching those later.):

While you're doing this - and perhaps you noticed on the bottom pins of the IC1 chip - the ground planes on the DoodleBug are very substantial. I hesitated to mention this before, because if you turn the heat up too high on your iron, you can fry the ADuM chip. However, you may want to turn up your iron while doing the passive parts. Be careful, because you can burn the PCB or parts. What you want is high-temperature and localized heat transfer - quick enough to melt the solder. If your iron is too cold, you'll find yourself heating up the entire ground planes on both sides of the PCB and never melting the solder. Be cautious, experiment with higher temperature settings, but don't go too far. I've found that adjusting in 50 deg. F. increments is sufficient to find a higher temp that works. You might also let your iron "re-charge" between soldering pads that are connected to the ground plane. One or two in a row may cool down your iron's tip and letting it sit for a few minutes should bring that temperature back. Of course, this description is for how I do it with a Hakko 936. Simpler soldering irons may not let you adjust at all; more sophisticated ones may control temperature at the tip - precluding any relaxing to gain the heat back on the tip. Your mileage may vary, in other words ...

This pic shows the 1206 SMD resistors soldered in place. Cross-reference the BOM with the silkscreen on the PCB - make certain you don't get the values mixed up. Also, try to solder so that the labeling is all in the same direction. It will help if trouble-shooting becomes necessary:

In this pic, I've soldered the ferrite ("L" parts) parts in place, having turned the PCB ninety-degrees to solder the L4 ferrite..

Here we see the PCB with the ADuM chip and all of the 1206 SMD parts complete.

file last changed:Friday, October 31, 2014 7:22:06 AM
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